Fix unstable order/flickering of "shown in" space view list on select…

…ion (#2327)

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### What

List of space views is now a BTreeMap, not a HashMap
Fixes #2193
* #2193

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)


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PR Build Summary: https://build.rerun.io/pr/2327

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Docs preview: https://rerun.io/preview/e376b61/docs
Examples preview: https://rerun.io/preview/e376b61/examples
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crates/re_viewer/src/ui/blueprint_load.rs

@@ -1,3 +1,5 @@
+use std::collections::BTreeMap;
+
 use ahash::HashMap;
 
 use re_data_store::{query_timeless_single, EntityPath};
@@ -111,7 +113,7 @@ fn load_viewport(
         .map(|(k, v)| (*k, v.clone()))
         .collect();
 
-    let known_space_views: HashMap<_, _> = space_views
+    let known_space_views: BTreeMap<_, _> = space_views
         .into_iter()
         .filter(|(k, _)| viewport_layout.space_view_keys.contains(k))
         .collect();

crates/re_viewport/src/auto_layout.rs

@@ -51,7 +51,7 @@ pub(crate) fn tree_from_space_views(
     ctx: &mut ViewerContext<'_>,
     viewport_size: egui::Vec2,
     visible: &std::collections::BTreeSet<SpaceViewId>,
-    space_views: &HashMap<SpaceViewId, SpaceViewBlueprint>,
+    space_views: &BTreeMap<SpaceViewId, SpaceViewBlueprint>,
     space_view_states: &HashMap<SpaceViewId, SpaceViewState>,
 ) -> egui_tiles::Tree<SpaceViewId> {
     let mut space_make_infos = space_views

crates/re_viewport/src/space_view_highlights.rs

@@ -1,4 +1,5 @@
-use ahash::HashMap;
+use std::collections::BTreeMap;
+
 use egui::NumExt;
 use nohash_hasher::IntMap;
 
@@ -14,7 +15,7 @@ use crate::SpaceViewBlueprint;
 pub fn highlights_for_space_view(
     selection_state: &SelectionState,
     space_view_id: SpaceViewId,
-    space_views: &HashMap<SpaceViewId, SpaceViewBlueprint>,
+    space_views: &BTreeMap<SpaceViewId, SpaceViewBlueprint>,
 ) -> SpaceViewHighlights {
     re_tracing::profile_function!();
 

crates/re_viewport/src/viewport.rs

@@ -2,6 +2,8 @@
 //!
 //! Contains all space views.
 
+use std::collections::BTreeMap;
+
 use ahash::HashMap;
 use itertools::Itertools as _;
 
@@ -32,7 +34,9 @@ pub type VisibilitySet = std::collections::BTreeSet<SpaceViewId>;
 #[serde(default)]
 pub struct Viewport {
     /// Where the space views are stored.
-    pub space_views: HashMap<SpaceViewId, SpaceViewBlueprint>,
+    ///
+    /// Not a hashmap in order to preserve the order of the space views.
+    pub space_views: BTreeMap<SpaceViewId, SpaceViewBlueprint>,
 
     /// Which views are visible.
     pub visible: VisibilitySet,
@@ -677,7 +681,7 @@ fn visibility_button_ui(
 struct TabViewer<'a, 'b> {
     viewport_state: &'a mut ViewportState,
     ctx: &'a mut ViewerContext<'b>,
-    space_views: &'a mut HashMap<SpaceViewId, SpaceViewBlueprint>,
+    space_views: &'a mut BTreeMap<SpaceViewId, SpaceViewBlueprint>,
     maximized: &'a mut Option<SpaceViewId>,
 }